This invention relates to television receiver apparatus of the type which is capable of receiving and displaying a video picture derived from transmitted video signals, or alphanumeric data information derived from alphanumeric data program signals which are multiplexed with the video signals; and, more particularly, to such apparatus wherein all of the alphanumeric data programs which are transmitted on a given television broadcast channel are displayed, such as by titles or code, so as to apprise a user of those alphanumeric data programs which are available. This invention also particularly relates to such a display wherein the particular alphanumeric data program which then is being received is indicated, and the particular alphanumeric data program which the user may select also is indicated.
Since the cathode ray tube of a typical television receiver, such as a so-called home-entertainment television receiver, is capable of being controlled to display either video pictures of a scene, animation, or the like (referred to herein as entertainment pictures) or alphanumeric data information, such as letters, numerals, symbols, or the like (referred to as data information), it has been proposed that alphanumeric data signals be multiplexed with conventional video signals such that a broadcasting channel may transmit both video picture information and alphanumeric data information. Such alphanumeric data information may be associated with various data programs, such as a weather forecast, stock quotations, road condition information, consumer price information, and the like. This information may be displayed as words, numerals, symbols, or the like on the display screen of a television cathode ray tube.
The alphanumeric data information that is to be multiplexed with the composite video signals may be superimposed onto at least one horizontal line interval in each video frame and, more particularly, onto a horizontal line interval in each field interval. For example, horizontal line intervals #20 and #283 (referred to as line intervals 20H and 283H) of each frame normally do not contain useful video information. Hence, the alphanumeric data information may be inserted into line intervals 20H and 283H without loss of video picture information. In the aforementioned proposal, two hundred of these line intervals are used to transmit all of the alphanumeric information contained in a particular alphanumeric data program. Since only one line interval in each field is provided with such alphanumeric data signals, the complete transmission of an entire alphanumeric data program requires the transmission of two hundred fields. Then, after one alphanumeric data program is transmitted, another alphanumeric data program is transmitted in the next-following two hundred fields.
The alphanumeric data program signals which are transmitted in the 20H and 283H line intervals of each frame, that is, the alphanumeric data program signals which are transmitted in the assigned horizontal line interval in each field, contain a multi-bit data signal as well as various other multi-bit control signals. For example, the control signals may include a 16-bit write clock synchronizing code, an 8-bit framing code, an 8-bit service identification code, and two 8-bit program identification codes. In the assigned line interval in one frame, such as the 20H line interval, the alphanumeric data signals may be a 240-bit color code; whereas in the assigned line interval in the other field, i.e. the 283H line interval, the alphanumeric data signal may be formed as a 248-bit information signal. The line interval containing the color code also contains an 8-bit line code. Thus, in the aforementioned proposal, the alphanumeric data program signals which are contained in the 20H or 283H line interval are formed as 296-bit signals, consisting of a synchronizing code, a framing code, a service identification code, a program identification code, a line code, and either a color code or alphanumeric data. These alphanumeric information signals may be suitably separated from the composite video signals, and decoded so as to display the alphanumeric information on the screen of the cathode ray tube. The type of display is determined by the aforementioned service identification code, which may designate a so-called C-representation, wherein a fixed picture of alphanumeric characters is displayed across the entire display screen; an S-representation, wherein two rows of alphanumeric characters are displayed at the lower portion of the display screen, these two rows being updated with new information periodically; or T- or X-representation, wherein the alphanumeric characters are scrawled acro-s the entire display surface of the display screen, in the horizontal or vertical directions.
In the proposed alphanumeric data program transmission/reception system, a maximum of 256 different alphanumeric data programs may be transmitted. However, since two hundred field intervals are needed to transmit one entire program, approximately 3.3 seconds are required for the transmission of each program. If a television broadcasting channel is provided with N multiplexed alphanumeric data programs, then the time required for the transmission of the complete repertoire of that television broadcasting channel is equal to 3.3.times.N seconds. Typically, N=10. If a user wishes to observe program #1, and if the last field containing program #10 has just been transmitted, then a delay, or waiting period of 3.3 seconds must pass before the viewer observes this selected program. However, if the viewer wishes to observe program #10, and the first field containing program #1 is being transmitted, then a waiting period of 33 seconds must pass until the selected program is observed. If only the selected program is displayed on the cathode ray tube screen, then a substantial period of time will expire (up to 33 seconds in the aforementioned example) until an alphanumeric data program is observed. This unusual delay may result in concern by the viewer that his apparatus is not operating properly.
The aforementioned difficulties are particularly pronounced if the viewer is not provided with any display representing the alphanumeric data programs which are available on the broadcasting channel then being received by the television receiver. For example, the viewer may select a particular alphanumeric data program which he wishes to observe, which selected program is not transmitted on the television broadcasting channel to which his television receiver is tuned. This fact may not be readily known to the viewer, unless a listing of the alphanumeric data programs which are multiplexed onto that broadcasting channel is displayed. If 256 such alphanumeric data programs are selectable (as mentioned above), it may become quite difficult for the viewer to (a) tune his television receiver to the proper television broadcasting channel on which the alphanumeric data program which he has selected is transmitted, and (b) await the ultimate display of that selected program. Furthermore, it is helpful if, in addition to displaying the list of alphanumeric data programs which are transmitted on the television broadcasting channel then being received, an indication is provided to apprise the viewer of the particular program which is being transmitted, so that he may determine the delay which must be encountered before his selected program is displayed.